AlgoDaily - Longest Palindromic Substring

Longest Palindromic Substring (Hard)

Good afternoon! Here's our prompt for today.

You may see this problem at Facebook, Godaddy, Symantec, Ibm, Glassdoor, Segment, Pipedrive, Servicenow, Cvent, Veeam, Veeva Systems, and Motorola.

We're given a string that's a mixture of several alphabetical characters.

JAVASCRIPT

1const str = "algototheehtotdaily";

Could you write a method to find the longest substring that is considered a palindrome? In the above example, it would be "totheehtot".

Where there are multiple longest palindromic substrings of the same length, for example in "abracadabra" ("aca" and "ada"), return the first to appear.

Constraints

The string can be empty, in which case return an empty string
The string will consist of only lowercase alphabets
Expected time complexity : O(n^2)
Expected space complexity : O(n^2)

xxxxxxxxxx
​
 
var assert = require('assert');
​
const longestPalindrome = (str) => {
  // fill in
  return '';
};
​
try {
  assert.equal(longestPalindrome(''), '');
​
  console.log('PASSED: ' + "`longestPalindrome('')` should return `''`");
} catch (err) {
  console.log(err);
}
​
try {
  assert.equal(longestPalindrome('algodaily'), 'a');
​
  console.log(
    'PASSED: ' + "`longestPalindrome('algodaily')` should return `'a'`"
  );
} catch (err) {
  console.log(err);
}
​
try {
  assert.equal(longestPalindrome('gymmyg'), 'gymmyg');

OUTPUT

Results will appear here.